ArduPlane 2.73 released

I've just released ArduPlane 2.73 as a bug fix release for several important bugs in 2.72

The main reasons for this release are:

  • fixed a noise and scaling problem with airspeed sensors
  • fixed a potential flyaway problem with the L1 navigation controller
  • improved handling of poor GPS velocity for attitude correction

This release does not contain the new attitude controllers that I previously said would be in 2.73. Paul and I decided that it would be better to hold those over to the next release, and get this release out with just the above critical bug fixes.

The airspeed problem stemmed from a changed introduced in 2.72 to make ArduPlane automatically scale analog inputs with board voltage. That change was good for voltage and current sensing, but it added a lot of noise to airspeed sensing as the 3DR airspeed sensor is ratiometric (the sensor output scales with the supply voltage). The fix was to add support for ratiometric analog inputs. This release also fixes a bug in the airspeed ratio handling. To confirm the fix I have been driving around in my car with an APM2 and PX4 logging airspeed and GPS speed - that test confirmed the airspeed sensing is now accurate.

The flyaway bug in L1 was caused by an unusual situation where the previous waypoint was equal to the next waypoint, which can happen when a mission is interrupted and restarted. The L1 controller would then level the wings and fly straight ahead until the operator intervened. The bug fix was to make the L1 controller detect this situation and track directly to the next waypoint. I don't think many users would have seen this bug, but it definitely could happen and warranted a bug fix release.

The GPS handling bug was related to the MTK GPS, which can be very slow to report loss of GPS lock, which could lead to very poor attitude from DCM and even a crash if the plane tries to turn while the GPS is reporting incorrect velocity information. The fix was to watch the satellite count, and stop using the GPS velocity for accelerometer correction when it had less than 6 satellites. This is selectable with the new AHRS_GPS_MINSATS option.

Other changes

While this release doesn't have the new attitude controllers I decided to leave in some other smaller changes that have been made since the 2.72 release that I consider to be low risk, including:

  • fix the PX4 barometer driver to run at full rate
  • fixed handling of a saturated compass on PX4
  • added COMPASS_ORIENT option to support external compasses
  • fixed the compass in HIL simulation
  • added GCS messages to flash logs
  • allow 3D accel calibration over MAVLink
  • Added new ELEVON_OUTPUT option
  • removed MANUAL_LEVEL option (manual level is now always on)
  • improved pitch handling when inverted

Of these, perhaps the most useful is the ELEVON_OUTPUT option. That makes it possible to setup your transmitter with normal aileron/elevator and get the APM to do a software elevon mixer on output. That gives better control in FBWA mode than the previous elevon options.

I recommend that all users of 2.72 upgrade to 2.73. Happy flying!

Cheers, Tridge




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  • I test flew 2.73 on the x8 today. The new Elevon_Output function didn't work well and gave me sluggish controls. I almost lost control a couple times from control surface glitches. I switched back to using the radio for Elevon programming and it worked normally again, same firmware 2.73. 

    I finally got FBW to work. I had to crank up the Max Bank to 60 degrees to get about 30 degrees bank at full stick deflection. I increased the Servo_Roll_P until it started oscillating, then back down to 10.0. 
    So now it works, but I find it odd that the max roll angle has to be so high. I haven't analyzed the logs yet to see exactly what the max bank I ended up with was, but it certainly wasn't 60!
  • Hi!

    I just want to thank the developers for doing a great work!

    I have been struggling with my X-8 for a long time, main problem was the settings to get the navigation to work properly...

    Then i loaded 2.73 and VOILA the wing is navigating right out of the default code (i only adjusted stab PID, max bank, speed and those std. param.)


    Vid. of my X-8 With some other issues i had as well ;-)

  • Hello,


    I was checking all the function with release 2.73 and I have one question about failsafe.


    I remember that there was an option in the Mission planer where you could set up a short failsafe option (1sec) that change your fly mode to RTL in short time avoiding cycle mode.

    The second option was a 20sec failsafe mode.


    I tested both of them,  but the short failsafe mode does not work although I have checked in the short failsafe box and the FS_short_actn parameter is in 1


    It is always changing to RTL mode in 20 sec.



    Short failsafe action (ArduPlane:FS_SHORT_ACTN)

    The action to take on a short (1 second) failsafe event

    • Values








    Thank a lot; Leopoldo

  • I have never had luck trying to repeat a mission UNLESS I reset the mission either via the restart mission button on MP or using my gear channel switch I have setup for resetting the mission. Works every time using either of those methods.

  • The RLog

    2013-05-14 12-10-04.rlog
  • the Tlog

    2013-05-14 12-10-04.tlog
  • I´m not sure if I had the flyaway bug or another bug with 2.72. In the figure can be show that only could do the mission the first time because the alt_error_nav was increasing! despite it was the same mission. The other 2 times, in auto mode  the X8 was trying to go much higher above the waypoints. Any help is apreciated.



    Mission Planner won’t load 2.73?

    What did I do wrong? I have MP 50.




  • Can Arduplane run on the new PX4 ?

    If this is not the place for this question please forgive me.

  • Hi Andrew,

    Great work on the development - you guys really are doing a fantastic job.

    Can you (or someone else) please help with approach/glide settings... I can't seem to find the solution to:

     > I would like to set up a long approach, motor-off, with APM using pitch control to maintain a predefined airspeed. The approach is over several waypoints and I would like to adjust the target airspeed for each leg (reducing from ~45kts to 20kts in stages over ~5 legs). What parameters in MP do I need to adjust at each WP in order to achieve this?

    The most important aspect is 'motor-off'.

    Apologies if this isn't the correct place to post.

    Many thanks,


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